In the production of oil from an oil-bearing formation, numerous problems may be encountered. If the formation is of a loosely consolidated nature, the produced fluids can be expected to contain some particulate matter. It is, of course, undesirable to produce such particulate matter with the production fluids because of abrasion of the production tubing, valves, and other equipment used. In such instances, it is necessary to avoid production of such sand and other particulate matter with the fluids. In other instances, the formation may have a low permeability which will result in low production levels. In such instances, it is necessary to take measures to increase the flow of fluid from the formation.
The physical properties of the oil also will vary substantially. For example, some oils have a relatively low viscosity (light oils) and flow freely into the well casing for recovery. Typical of such oils are those found in the Middle East and Eastern United States. In some areas, the oil is more viscous and generally is referred to as a heavy oil. Typically, oils produced in Alaska and California are heavy oils. When a formation is encountered containing a heavy oil, which is too viscous to flow freely into the casing for recovery, it is necessary to either accept a low production rate or take measures to enhance the recovery rate. A typical enhancement measure comprises heating the oil in the formation to reduce its viscosity. The most common heating method utilizes the direct injection of steam into the formation. Typically, one of two methods is utilized. In one method, steam is injected into the formation through one or more injection wells which are located peripherally about a production well. In the other method, steam is injected directly into a production well for a fixed period of time to heat the formation, after which production from the well is resumed.
In addition to subterranean formations, there also are outcropping, oil-bearing formations in which a portion of the formation is close to the surface and which may have a significant portion exposed to the atmosphere at the surface. Over the millenniums, substantially all of the lower boiling point (light ends) constituents of the oil have evaporated. Such oil is essentially non-pumpable having a semi-solid or tar-like consistency. Substantially little effort has been made to recover oil from these formations because of environmental concerns. More particularly, it has been feared that any attempt to recover oil from these formations could cause increased, uncontrolled oil seepage to the surface at surrounding areas with unintended environmental damage. Clearly, it would be beneficial if there was a way to recover oil from such formations, provided such recovery could be accomplished without adversely affecting the environment.